1. Dipartimentodi Scienze Statistiche, Facoltá di Ingegneria dell'Informazione, Informatica e Statistica; Sapienza Universitá di Roma; Rome; Italy
2. Department of Methodology and Statistic; Tilburg University; Tilburg; The Netherlands
3. Department of Gerontology and Geriatrics; Leiden University Medical Center; Leiden; The Netherlands
4. Department of Medical Statistics and Bioinformatics; Leiden University Medical Center; Leiden; The Netherlands